Question

how can agriculture negatively affect the quality of water? they can increase the water supply by over - irrigation. they can deplete the water of nutrients. they can overuse fertilizers and insecticides. they can decrease weathering and erosion of soil.

Explanation:

Overusing fertilizers and insecticides in agriculture leads to runoff containing these chemicals into water bodies, causing pollution (e.g., eutrophication from excess nutrients, toxicity from pesticides) which degrades water quality. The other options are incorrect: over-irrigation affects water quantity/salinity not quality directly, agriculture adds nutrients (not depletes) to water, and it increases (not decreases) soil erosion which also harms water quality.

Answer:

They can overuse fertilizers and insecticides.